GB2072622A

GB2072622A - Roll film cassette

Info

Publication number: GB2072622A
Application number: GB8011180A
Authority: GB
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1980-04-02
Filing date: 1980-04-02
Publication date: 1981-10-07

Abstract

A film cassette comprises a substantially cylindrical body shell 1 fitted at each end with circular end caps and having a mouthpiece comprising a lengthwise gap defined by inner and outer parallel extension flanges so located that film material will leave the cassette through the mouthpiece tangentially to the body shell of the cassette. The extension flanges are lined with strips of a light-sealing fabric 5, 8, such as velvet, which provide a light trap. The body shell of the cassette has a step 9 which is in contact with the strip of light-sealing fabric 5 lining the outer extension flange and which extends parallel to the axis and along the greater part of the body of the cassette and accommodates the fabric so that the surface of the fabric is flush with the inner surface of the body shell of the cassette. The body shell may be of metal or plastics and a second step may be provided for the inner end of the other strip of light-sealing fabric 8. The use of the step reduces the distortion of the film material when it is left partially withdrawn from the cassette for a period of time. <IMAGE>

Description

SPECIFICATION Film cassette This invention relates to a photographic film cassette which encloses a roll of film on a spool.

Cassettes of this type are used in cameras, the leading edge of the film being threaded to the take-up spool in the camera. After the camera has been closed the remainder of the film is fed past the exposure chamber on to the take-up spool and then after all of it has been exposed it is led back again into the cassette and the cassette is then removed from the camera so the photographic film can be processed.

Such cassettes comprise a cylindrical shell with a lengthwise flanged gap which is lined with a lightsealing fabric material such as velvet. This gap constitutes the mouthpiece out of which the film material passes and through which the film material is fed back. Each end of the cassette has a flanged cap which fits over the cylindrical shell. A hole is present in the centre of each end cap through one of which protrudes one end of the spool on to which the photographic film material is wound, the other end of the spool usually being level with the end cap.

The spool has towards each of its ends two flanges which abut the two end caps so forming a light seal.

At one time it was usual to align the mouthpiece at about 30 to a radial intersection of the cassette but some distortion of the film was observed if the film remained for some time in the same position, partially out of the cassette. Thus in recent years it has become more usual to set the mouthpiece tangentially onto the cassette. However because of the presence of the light-sealing fabric in the mouthpiece there is still some distortion of the film material when it is left partially withdrawn from the cassette for a period of time.

We have discovered a way of reducing this defect.

According to the present invention there is provideo a photographic film cassette adapted to contain a roll of film on a flanged spool, which cassette comprises a substantially cylindrical body shell fitted at each end with circular end caps, the mouthpiece of the cassette being a lengthwise gap defined by inner and outer parallel extension flanges so located that film material will leave the cassette through the mouthpiece substantially tangentially to the body shell of the cassette, the said extensions being lined with strips of a light-sealing fabric to provide a light-trap, the body shell of the cassette comprising a step which abuts the strip of light-sealing fabric lining the outer extension flange, said step extending parallel to the axis and along the greater part of the body of the cassette and accommodating the fabric so that the surface of the fabric is substantially flush with the inner surface of the body shell of the cassette.

Preferably the light-sealing fabric is a pile material, for example velvet.

The maximum depth of the step is usually in the range 0.5 to 2 mm which corresponds to the thickness of the fabric strip in 35 mm cassettes.

In a first embodiment of the invention both the internal and external surfaces of the body shell of the cassette are cylindrical except in the immediate region of the lengthwise gap, the outer extension flange being so formed to accommodate the fabric strip. A cassette of this first embodiment of the invention is shown in Figures 4 and 5 attached hereto.

In a second embodiment of the invention the whole of the external surface of the body shell of the cassette is substantially cylindrical but a step is formed inside the body either by a moulding process if the cassette is made of a plastics material, so forming a step which is integral with the body shell of the cassette or by preparing a preformed step which is caused to adhere to the inner body wall of the body shell. In this embodiment preferably the depth of the step is greatest adjacent to the strip of light-sealing fabric and gradually decreases to zero over the quadrant of the body shell adjacent to the outer tangential extension.

In a third embodiment of the invention the step is formed as a depression in the body shell of the cassette, the depression being greatest in depth adjacent to the strip of light-sealing fabric and gradually decreasing in depth to zero over the quadrant of the body shell adjacent to the outer tangential extension.

In this embodiment of the invention the body shell is composed of a plastics material which can be moulded or press formed or most preferably is composed of a metal and the step is formed during the pressing process to form the body shell.

In this embodiment the step in the body shell being formed by a moulding or pressing process preferably the thickness of the body shell is substantially independent of the point at which the radial depth of the step is measured.

A cassette of the third embodiment is shown in Figures 1 to 3 attached hereto.

Afurther advantage of the cassette of these alternative embodiments is that it tends to strengthen the mouthpiece of the cassette and prevent it becoming distorted in use.

Preferably a second step is provided to accommodate the thickness of the fabric lining the inner tangential extension so that the surface of the fabric strip abutting the second step is substantially flush with the inner surface of the body portion.

The accompanying drawings will serve to illustrate the invention. In the Figures the same numbers have the same signification.

Figure 1 is a side elevation of the cassette according to the present invention.

Figure2 is a cross-sectional end view of the cassette of Figure 1 along the line X - X.

Figure 3 is the same view as Figure 2 but showing a film spool therein with the leading end of the film protruding from the cassette.

Figure 4 is a cross-sectional end view of another cassette according to the present invention.

Figure 5 is a cross-sectional end view of a third cassette according to the present invention.

Figure 1 shows a cassette of the third embodiment of the present invention.

In Figure 1 the cassette consists of a pressed metal body shell 1 having at the ends two grooved circular end caps 2 and 3. Extending tangentially from the shell 1 is the top flange extension 4 covered with a black velvet strip 5.

Present on the surface of the body shell lisa pressed indentation 6 which as shown in Figure 2 forms a step 9 inside the body shell.

In Figure 2 there is also shown the short bottom flange extension 7 covered with a black velvet strip 8.

As can be seen in Figure 2 the maximum depth of the step 9 is the same as the thickness of the velvet pile which in practice in a 35 mm cassette is about 1 mm thick.

Figure 3 shows a spool 10 in place in the cassette body shell 1. Unwinding from the spool 10 is a strip offilm 11.

As can be seen in this Figure the film passes smoothly out of the cassette without any kinking or buckling due to the presence of the velvet strip 5. If the step 9 had not been present, due to the clock-springing effect of the resilient film material the film material would have been pressed against the inner wall of the cassette until it would be forced down over the strip 5 to emerge from the cassette.

This would have caused the film to buckle as it was forced down to pass the strip 5. If the film was left in the camera in this state so that there was a buckle in one particular frame, this buckle would become a permanent distortion and when this part of the film was exposed part of the frame could be out of focus.

In the cassette of the present invention buckling or kinking of this type does not occur as can be seen from Figure 3.

In Figure 4 which shows the cassette of the first embodiment the top flange extension 4a is lined with a velvet strip 5a and the bottom flange extension 7a is lined with a velvet strip 8a. The step in this cassette is formed by raising the top flange extension 4a from the surface of the body shell 1 of the cassette so that the velvet strip 5a is flush with the inner surface of the body shell 1.

Figure 5 shows a cassette of the first embodiment which is very similar to that of Figure 4 except that in this not only has the outer top flange 4b lined with a velvet strip 5b been raised above the level of the body shell 1 to form a step but also the inner flange extension 7b lined with a velvet strip 8b has been raised above the level of the body shell 1. This construction means that both the velvet strips 5b and 8b are flush with the inside of the body shell 1 of the cassette.

Claims

1. A photographic film cassette adapted to contain a roll of film on a flanged spool, which cassette comprises a substantially cylindrical body shell fitted at each end with circular end caps, the mouthpiece of the cassette being a lengthwise gap defined by inner and outer parallel extension flanges so located that film material will leave the cassette through the mouthpiece substantially tangentially to the body shell of the cassette, the said extensions being lined with strips of a light-sealing fabric to provide a light-trap, the body shell of the cassette comprising a step which abuts the strip of light-sealing fabric lining the outer extension flange, said step extending parallel to the axis of the body and along the greater part of the body of the cassette and accommodating the fabric so that the surface of the fabric is substantially flush with the inner surface of the body shell of the cassette.

2. A photographic film cassette according to claim 1 wherein the light-sealing fabric is velvet.

3. A photographic film cassette according to either claim 1 of claim 2 wherein both the internal and external surfaces of the body shell of the cassette are cylindrical except in the immediate region of the lengthwise gap, the outer extension flange being so formed to accommodate the fabric strip.

4. A photographic film cassette according to either claim 1 or claim 2wherein substantially the whole of the external body shell of the cassette is cylindrical but a step is formed inside the body either by a moulding process if the cassette is made of a plastics material, so forming a step which is integral with the body shell of the cassette or by preparing a preformed step which is caused to adhere to the inner body wall of the body shell.

5. A photographic film cassette according to claim 4 wherein the depth of the step is greatest adjacent to the strip of light-sealing fabric and gradually decreases to zero over the quadrant of the body shell adjacent to the outer tangential extension.

6. A photographic film cassette according to either claim 1 or claim 2 wherein the step is formed as a depression in the body shell of the cassette, the depression being greatest in depth adjacent to the strip of light-sealing fabric and gradually decreasing to zero over the quadrant of the body shell adjacent to the outer tangential extension.

7. A photographic film cassette according to claim 6 wherein the body shell is composed of a plastics material which can be moulded or presS formed.

8. A photographic film cassette according to claim 6 wherein the body shell is composed of metal and the step is formed during the pressing process to form the body shell.

9. A photographic film cassette according to any one of claims 6 to 8 wherein the thickness of the body shell is substantially independent of the point at which the radial depth of the step is measured.

10. A photographic film cassette according to any one of claims 1 to 9 wherein a second step is provided to accommodate the thickness of the fabric lining the inner tangential extension so that the surface of the fabric strip abutting the second step is substantially flush with the inner surface of the body portion.

11. A photographic film cassette according to claim 1 substantially as hereinbefore described with reference to the accompanying drawings.